The strip of dunes along the Belgian coastline forms a rather fragmented landscape. Some of the remaining dune habitats received the legal statute of nature reserve and are managed to maintain or to restore high biodiversity. Large herbivores are introduced in some of the dune reserves as a management tool. They play a major role in these ecosystems. Fundamental research as well as management monitoring try to answer the many questions that arise on the impact of the large herbivores on their environment on the one hand, and the influence of the environment on the grazers’ behaviour on the other hand. The study presented here deals with the latter. In particular, we focus on the behaviour and habitat use of horses, free ranging in different, spatially heterogeneous dune areas. Donkeys, Shetland ponies and Haflinger horses are our study animals, each grazing in one of the dune areas near the French-Belgian boarder. Data on the animals’ behaviour were collected through continuous focal animal observation. From the large amount of observations it became obvious that equids are true “grazers”, spending most of their daytime to grazing (48-71%). Resting, walking and standing alert take most of the remaining time. This pattern is strongly affected though by seasonal variation, with an increased grazing time in the seasons with low plant productivity. We further examined how the equids use their heterogeneous environment. As expected, the horses do not show a random distribution pattern. Although the three study areas differ in vegetation type availability and pattern, we can conclude that all equids graze the most in grassy vegetation types and in roughages. Scrubs and woodland are not or only marginally grazed. For both donkeys and Shetland ponies the habitat use varies through the year: when forage quality and quantity in the grassy habitat types deplete in the non-productive seasons, the equids increase their grazing time in the other habitat types. Large herbivores have a great impact on the vegetation through ...